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    <title>Document</title>
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    <!-- table表示表单标签 -->
    <table border="">
<!-- tr表示行，有几行就有多少横向的单元格 -->
<!-- td表示列，有几列就有多少纵向的单元格 -->
        <tr>
            <td>a1</td>
            <td>b1</td>
            <td>c1</td>
<!--rowspan表示纵向合并单元格-->
            <td rowspan="2">d1</td>
        </tr>
        <tr>
            <td>a2</td>
            <td>b2</td>
            <td>c2</td>
        </tr>
        <tr>
            <td>a3</td>
            <td>b3</td>
            <td>c3</td>
            <td>d3</td>
        </tr>
        <tr>
            <td>a4</td>
            <td>b4</td>
<!--colspan表示横向合并单元格-->
            <td colspan="2">c4</td>
        </tr>
    </table>
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